WASHINGTON (Reuters) - The Congress has resolved almost nothing of consequence since 2010, failing to complete what were once basic responsibilities for roads, schools, farms and the U.S. mail.

Asking the Republican-controlled House of Representatives and the Democratic-led Senate to agree on militaryaction - already a controversial issue both within and between the parties - injects a new dose of uncertainty into Washington's reaction to the Syria crisis.

Because Congress will not even begin floor debate until September 9 at the earliest, a question mark will hang over Washington's Syria policy for weeks, punctuated by emotional and probably bitter debate.

That became evident on Saturday immediately after President Barack Obama's surprise announcement that he would seek authorization for limited military strikes inSyria from members of Congress, many of whom, he has complained, reflexively oppose anything he proposes.

No one knowledgeable about Congress was willing to predict with any confidence how it would deal with a resolution to permit strikes inSyria.

The uncertainty is compounded by Obama's often strained and distant relationship with Congress.

A House Democratic aide, on condition of anonymity, said "the vote will depend on the Republicans" because Democrats "will be split down the middle."

Asked how the votes might go in the House and Senate, Republican Senator Bob Corker of Tennessee said he thought it could be "problematic."

PUBLIC OPINION FACTOR

Some members "may not understand what's happening" inSyria, he told CNN, and "the American people today are not supportive of this. ... I do not think the country is there."

Jon Alterman, director of the Middle East Program at the Center for Strategic and International Studies, said: "The decision to get Congress on board when hasn't had a huge amount of success working with Congress strikes me as a gamble.

"The president and secretary of state have tried to signal resolve, but the question becomes - what happens when they don't get the support that they want and what does that mean about the administration's ability to lead the country?"

The Syria issue is highly complex politically, causing divisions both within and between the parties, particularly at the extremes.

Some traditionally liberal Democrats, including members of the Congressional Black Caucus, have been skeptical of intervention, with several dozen Democrats signing a letter on Thursday worrying about getting into an "unwise war."

Some of the most conservative Republicans, such as Michigan Representative Justin Amash, have also expressed skepticism.

Supporters of intervention, including Senator John McCain of Arizona and Senator Lindsey Graham of South Carolina, stopped short of endorsing an authorization, saying in a joint statement that they worried that Obama's limited plan for military strikes might not go far enough to satisfy them.

The authorization request, narrowly worded as a response to the use of chemical weapons or other weapons of mass destruction, came from the White House late on Saturday in the form of a resolution which will require approval of both houses of Congress.

RESOLUTION COULD GET SLOWED DOWN

Attempts to amend the resolution or to use procedural means to slow it down are not unlikely, and Obama would need considerable Republican help to get it passed.

"Ironically, Obama may be saved by congressional Republicans," said Darrell West, director of governance studies at the Brookings Institution. "They tend to be more hawkish on foreign policy. I could see a large number of Democrats voting against it because they are more skeptical of foreign involvements."

Underscoring the division was immediate discord over the timing of Congressional deliberations on Syria, particularly the decision by the House leadership to wait until the end of the summer recess on September 9 to get going, instead of returning to Washington on Tuesday or sooner.

While the Senate Foreign Relations Committee said late on Saturday it would begin hearings next week beforeCongress officially returns, no similar plan had been announced by the House.

"Congress should return to Washington immediately and begin to debate this issues," said Senator Marco Rubioof Florida, considered a likely Republican presidential contender in 2016.

The president has the authority under the Constitution to call Congress back in session "on extraordinary occasions," but so can the congressional leadership. Neither so far has taken that action.

Senior administration officials said Obama left it up to congressional leaders to decide whether to bring members back early because the administration wants to do classified briefings and make the case to Congressin the week ahead, and there were logistical issues with the Labor Day holiday on Monday and religious holidays in the middle of the week.

Though many members had urged Obama to consult with Congress, a few were critical of the decision.

"President Obama is abdicating his responsibility as commander-in-chief and undermining the authority of future presidents," said Republican Representative Peter King of New York, a member of the House Intelligence committee, who backs a military response inSyria. "The president does not need Congress to authorize a strike on Syria."

Even some Democrats who backed Obama said they would have preferred that he acted without Congress.

"I support the president's decision," said Democratic Senator Bill Nelson of Florida. "But as far as I'm concerned, we should strike inSyria today. The use of chemical weapons was inhumane, and those responsible should be forced to suffer the consequences."